This invention relates to electrophotographic copiers and duplicators and, more particularly to a waste container and an indicating system for warning a machine operator of impending overfilling of the waste container.
In the process of electrostatographic printing, an electrostatic charge pattern or latent image corresponding to an original document to be reproduced is recorded on an insulating medium. A viewable record is produced by developing the latent image with particles of granulated material to form a powder image thereof. Thereafter, the visible powder image is fused to the insulating medium, or transferred to a suitable support material and fused thereto. Development of the latent image is achieved by bringing a developer mix into contact therewith. Typical developer mixes generally comprise dyed or colored thermoplastic particles of granulated material known in the art as toner particles, which are mixed with carrier granules, such as ferromagnetic granules. When appropriate, toner particles are mixed with carrier granules and the toner particles are charged triboelectrically to the correct polarity. As the developer mix is brought into contact with the electrostatic latent image, the toner particles adhere thereto. However, as toner particles are depleted from the developer mix, additional toner particles (simply xe2x80x9ctonerxe2x80x9d hereafter) must be supplied. In this way, the concentration of toner in the developer mix is maintained substantially constant.
In developer subsystems that employ so-called trickle development, a small amount of fresh carrier is included with the supply of toner which is dispensed by a dispensing apparatus into the developer subsystem. Generally, this system employs an overflow system in the housing of the developer subsystem which maintains the sump at a constant volume. The carrier is often coated with materials that assist in creation of the toner""s triboelectric charge. It is necessary to control the average carrier age (i.e. time used in development) in order to maintain its effectiveness in assisting in the creation of triboelectric charge on the toner. The method of controlling average age is to continuously add fresh carrier and remove some of the used carrier as waste.
In machines where the removal and replacement of waste containers is a task performed by a Customer/User, it is highly desirable to have an accurate method for indicating when the waste container is full so that Customers/Users are not dissatisfied by replacing a waste container which is not fully used or by overflow of a full container.
Typically, waste containers, such as a bottle, tend to be made from polypropylene or polyethylene. A natural color is generally chosen because the bottle is used in conjunction with an optical sensor which indicates when the bottle is at its full capacity. These optical sensors consist of an emitter and a detector which detect when the bottle is full by looking through a view window on the bottle or through the bottle directly. A problem with such systems is that toner contamination on the view window can trigger false readings; when the inside of the bottle becomes dusty, the sensor misinterprets this condition as a full bottle.
An alternative method that has been used in this type of application involves counting the number of copies since the bottle was last installed. This approach is not only indirect, but also inaccurate due to a wide variation in the amount of waste developer generated per copy. The inaccuracy correspondingly causes frequent bottle replacements and higher service costs. A means is needed to detect when a waste container from a xerographic development process is full in order to prevent overflow and backup of waste into the developer subsystem. A means is also needed to detect if the waste container is not fully installed in order to prevent dumping of waste into the system or environment.
There is provided a sensing system for detecting a full condition within a waste developer system, said sensing system including a developer waste container for receiving and holding waste developer material comprising toner and carrier deposited therein from a developer system; a sensor assembly mounted exterior to the developer waste container, said sensor including a reed switch being responsive to the level of material in said developer waste container when the material in said developer waste container reaches a predetermined level.
Other features of the present invention will become apparent as the following description proceeds and upon reference to the drawings.